U.S. patent application number 14/502535 was filed with the patent office on 2015-10-15 for apparatus and method for optical-network monitoring.
The applicant listed for this patent is Alcatel-Lucent Deutschland AG, Alcatel-Lucent USA Inc.. Invention is credited to Nagaraj Prasanth Anthapadmanabhan, Joerg Hehmann, Michael Straub.
Application Number | 20150295641 14/502535 |
Document ID | / |
Family ID | 54265948 |
Filed Date | 2015-10-15 |
United States Patent
Application |
20150295641 |
Kind Code |
A1 |
Anthapadmanabhan; Nagaraj Prasanth
; et al. |
October 15, 2015 |
Apparatus and Method for Optical-Network Monitoring
Abstract
A method, apparatus, and system for network monitoring, and more
specifically for correlating downstream devices in an optical
network with downstream ports of an optical splitter through which
they are communicating with a central office. The downstream
devices operational on the network are indentified and listed in a
correlation table. Selected subsets of these devices are then
monitored, preferably by an ISM under the direction of a management
node, in a series of monitoring cycles until a satisfactory
correlation may be achieved. The correlation cycle may be performed
at startup, as needed, or on a periodic basis.
Inventors: |
Anthapadmanabhan; Nagaraj
Prasanth; (Bridgewater, NJ) ; Hehmann; Joerg;
(Weil der Stadt, DE) ; Straub; Michael;
(Maulbronn, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Alcatel-Lucent USA Inc.
Alcatel-Lucent Deutschland AG |
Murray Hill
Stuttgart |
NJ |
US
DE |
|
|
Family ID: |
54265948 |
Appl. No.: |
14/502535 |
Filed: |
September 30, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61978453 |
Apr 11, 2014 |
|
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Current U.S.
Class: |
398/25 |
Current CPC
Class: |
H04B 10/27 20130101;
H04B 10/0775 20130101; H04Q 11/0067 20130101; H04Q 2011/0083
20130101; H04B 10/272 20130101; H04B 10/079 20130101; H04B 10/0793
20130101 |
International
Class: |
H04B 10/079 20060101
H04B010/079; H04B 10/27 20060101 H04B010/27 |
Claims
1. A method of monitoring an optical network comprising a plurality
of downstream devices in optical communication with a network node
via an optical splitter, the method comprising: selecting a
plurality of subsets of downstream devices, wherein each subset of
the plurality of subsets has in it more than one but less than all
of the downstream devices in a collective-monitoring set consisting
of at least a portion of the plurality of downstream devices and
any dummy downstream devices necessary to give the set 2.sup.n
members, wherein n is a positive integer; executing a plurality of
port monitoring cycles, each cycle applying a subset of the
plurality of subsets, each executed port monitoring cycle
comprising: directing un-selected downstream devices to cease
upstream transmissions; and monitoring upstream activity on
downstream splitter ports to determine which ports are receiving
upstream transmissions; and reporting the monitoring results.
2. The method of claim 1, wherein the reporting is performed after
the results are obtained in each port monitoring cycle.
3. The method of claim 1, wherein each subset of the plurality of
subsets has in it one-half of the downstream devices in the
collective-monitoring set.
4. The method of claim 3, wherein the selecting a plurality of
subsets of downstream devices comprises: selecting a first subset
having one group comprising the one-half of the downstream devices
in the collective-monitoring set, wherein a group is one or more
downstream devices that are adjacent to each other in a sequential
listing of devices in the collective-monitoring set; and selecting
subsequent subsets by selecting for the next subset groups of
one-half the size of the group or groups of the previous subset,
each group consisting of one-half of each previously selected group
or one-half of each previously unselected group, until log.sub.2(n)
subsets have been selected.
5. The method of claim 1, further comprising executing a port
monitoring cycle for one or more individual downstream devices,
each port measurement cycle for an individual downstream device
comprising: directing the selected device to cease upstream
transmissions; monitoring upstream activity on downstream splitter
ports; and reporting the results.
6. The method of claim 1, further comprising directing downstream
devices to resume normal operation.
7. The method of claim 1, further comprising, prior to selecting a
plurality of subsets, determining the identity of downstream
devices operational on the optical network.
8. The method of claim 1, wherein the optical network is a PON
(passive optical network) and the downstream devices are ONUs
(optical network units).
9. The method of claim 1, wherein the measuring and reporting is
performed by an ISM (intelligent splitter monitor).
10. The method of claim 1, further comprising updating a
correlation table with the reported results.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present disclosure is related to and claims priority
from U.S. Provisional Patent Application Ser. No. 61/978,453,
entitled Splitter Monitoring in Optical Access Network and filed on
11 Apr. 2014, and is related to U.S. patent application Ser. No.
13/106,088, entitled Intelligent Splitter Monitor and filed on 12
May 2011, the entire contents of which are incorporated by
reference herein.
TECHNICAL FIELD
[0002] The present invention relates generally to the field of
communication networks, and, more particularly, to a method and
apparatus for associating optical splitter ports in an optical
communication network with CPEs or other end devices.
BACKGROUND
[0003] The following abbreviations are herewith expanded, at least
some of which are referred to within the following description of
the state-of-the-art and the present invention.
CPE Customer Premises Device
ISM Intelligent Splitter Monitor
NA Network Analyzer
OLT Optical Line Termination
OMM Optical Monitoring Module
ONT Optical Network Terminal
ONU Optical Network Unit
PIC Photonic Integrated Circuitry
PLOAM Physical Layer Operations, Administration, and
Maintenance
[0004] Many optical communication networks use a point to
multipoint topology, for example a PON (passive optical network).
In one example, a PON includes an OLT (optical line terminal)
located in a CO (central office) that connects with a downstream
optical splitter, which is usually remote from the CO, via a feeder
fiber. The optical splitter in turn connects with a number of PON
end devices such as ONUs (optical network units) via a
corresponding number of access fibers. An optical splitter may also
connect at one or more of its downstream ports to another optical
splitter instead of an end device creating a cascaded topology.
Similar topologies may be used for optical networks in other
implementations, for example data centers.
[0005] In a PON, downstream transmissions from the OLT pass through
the one or more optical splitters to the ONUs or other end devices.
In most cases each end device receives the same transmission and
extracts the portion intended for it. Upstream transmissions from
the end devices, in a PON sometimes referred to as CPEs (customer
premises equipment), use the same fiber and splitter path as
downstream transmissions.
[0006] An ISM (intelligent splitter monitor) may be installed in
the optical network. In a typical configuration, the downstream
ports of one or more optical splitters are monitored to determine
when an upstream transmission has arrived at a specific port. This
may be facilitated by, for example, a tap coupling on the fiber or
other communication channel connected at the downstream
optical-splitter port. Downstream transmissions may be similarly
monitored as well, although presently this is considered
unnecessary.
[0007] Note that the techniques or schemes described herein as
existing or possible are presented as background for the present
invention, but no admission is made thereby that these techniques
and schemes were heretofore commercialized, or known to others
besides the inventors.
SUMMARY
[0008] With the goal of providing a more energy-efficient optical
communication network, inventors have developed an ISM (intelligent
splitter monitor) and herein disclose certain inventive aspects of
it and the operation thereof. Note, however, that while an
improvement in efficiency is expected through the application of
these new ideas, no particular result is a requirement of the
present invention unless explicitly recited in a particular
claim.
[0009] In one aspect, a method of network monitoring includes
providing an ISM associated with at least one optical splitter in
an optical network, for example a PON, or employing an existing
ISM. The ISM should configured to be able to monitor a set, and
preferably all, of the downstream ports of the associated at least
one optical splitter for upstream traffic. The monitoring of each
downstream port may be accomplished, for example, using a tap
coupler on the optical channel downstream if the splitter. In
general the method applies to the mapping of monitored ports, but
unmonitored ports may in some instances be mapped by the process of
elimination.
[0010] In this aspect, the method includes determining which end
devices are communicating on the optical network, which is often
though not necessarily done in the course of normal operation even
if the mapping of the end devices to specific splitter ports is
unknown. A table or similar device is established or populated with
all of the currently reporting end devices and provision is made
for incrementally associating or disassociating each end device
with each known splitter port. In some cases the status of splitter
ports as monitored or unmonitored is also determined and recorded.
If any end devices may at this time be associated or disassociated
with specific splitter ports or groups of splitter ports that may
be recorded at this point as well.
[0011] In this aspect the method includes selecting a plurality of
the end devices and directs other end devices communicating on the
network to cease upstream communications, either until being
further directed or for definite or calculable period of time. The
selected plurality of CPEs may then be instructed to commence
upstream communications, although in many implementations the
process may simply rely on standard upstream communications without
further instruction.
[0012] The activity of the downstream splitter ports is then
monitored, and in the table or similar device the unselected end
devices are disassociated with the monitored ports that the ISM
apparatus reported active during the monitoring cycle. When the
monitoring has proceeded long enough for this to occur, the
silenced CPE may be allowed to resume communication.
[0013] In some embodiments, a determination may then be made as to
whether each end devices has been uniquely associated with a
monitored (or in some cases, unmonitored) splitter port. If all (or
all desired) end devices have been associated with a splitter port,
the process may be terminated. Once terminated, the correlation
cycle may be re-executed, for example, on a periodic basis or
re-initiated upon the occurrence of an event.
[0014] In these embodiments, if it is determined that the
association of end devices to splitter ports is not complete or at
an acceptable level, then the process continues with the selection
of an additional plurality of splitter ports. The additional
plurality of end devices should not be identical in composition
with a previously selected plurality. (This is not prohibited, but
as it would be likely to produce the same association result after
monitoring, in most cases it would be inefficient.)
[0015] In these embodiments, once the additional plurality of end
devices is selected, then the remaining end devices are directed to
cease upstream transmission and the monitoring, reporting, and
associating or disassociating steps are performed. The
determination of the level of association is then repeated and the
process either terminates or continues with the selections of a new
additional plurality of end devices.
[0016] In most implementations the number of end devices to be
associated will be greater than three or four, and the number of
additional pluralities selected for monitoring will depend on the
number of end devices. A preferred method of selecting the CPEs,
however, will usually keep the number of monitoring cycles to a
minimum.
[0017] In a preferred method of monitoring an optical network
having a plurality of downstream devices in optical communication
with a network node via an optical splitter, the method includes
selecting a plurality of subsets of downstream devices. In a
preferred embodiment, each subset of the plurality of subsets has
in it more than one but less than all of the downstream devices in
a collective-monitoring set consisting of at least a portion of the
plurality of downstream devices and in addition any dummy
downstream devices necessary to give the set 2.sup.n members,
wherein n is a positive integer.
[0018] In this embodiment, a plurality of port monitoring cycles
may then be executed, with each cycle applying a subset of the
plurality of subsets. In this embodiment, each executed port
monitoring cycle includes directing un-selected downstream devices
to cease upstream transmissions and monitoring upstream activity on
downstream splitter ports to determine which ports are receiving
upstream transmissions. The method further includes reporting the
monitoring results. The reporting is performed at the end of each
monitoring cycle, at the conclusion of all the monitoring cycles,
or at some other time according to the needs of a particular
implementation.
[0019] In this embodiment, a table or similar device may be updated
with the reported results and the unselected end devices are
disassociated with the monitored ports that the ISM apparatus
reported active during the monitoring cycle. When the monitoring
has proceeded long enough for this to occur, the silenced
downstream devices may be allowed to resume communication.
[0020] In some embodiments the selecting of a plurality of subsets
of downstream devices includes selecting a first subset having one
group comprising the one-half of the downstream devices in the
collective-monitoring set, wherein a group is one or more
downstream devices that are adjacent to each other in a sequential
listing of devices in the collective-monitoring set, and then
selecting subsequent subsets by selecting groups of one-half the
size of the group or groups of the previous subset, each group
consisting of one-half of each previously selected group or
one-half of each previously unselected group until log.sub.2(n)
subsets have been selected.
[0021] In some embodiments of the method, individual subsets having
only one downstream device as a member may be selected and
individual monitoring cycles be executed if necessary to complete a
correlation cycle.
[0022] In another aspect, an ISM includes a photodiode array and a
microcontroller arranged such that the activation of a photodiodes
can be reported by the microcontroller. The microcontroller may
include or be connected to a transmitter for this purpose. When
installed in an optical access network, the photodiodes in the
array are operatively associated with respective ports of a network
optical splitter and such that the photodiode is activated by an
upstream signal from a downstream device directed toward the port
associated with the photodiode.
[0023] In this aspect the microcontroller may also include or be
connected to a receiver for receiving, for example, management
signals directed at the microcontroller. In a preferred embodiment,
the ISM includes a power source such as a rechargeable battery. For
remote operation, a photocell may be provided to convert a received
optical signal into electrical power for storage in the
rechargeable battery. A power controller may be used to direct
electrical power from the photocell to the battery and to the
microcontroller as needed.
[0024] In operation, photodiodes are optically connected to the
respective optical channels between the optical splitter and the
downstream devices. Note these channels may be implemented in
actual fiber and fiber connectors, but are advantageously
implemented partially or completely in semiconductor chips such as
a PIC.
[0025] In order to identify which downstream devices are associated
with which splitter ports, some of the downstream devices are
selectively turned off or silenced while others are instructed to
transmit. A standard measurement operation works well for this
purpose. A network node may include a management module for
determining which devices are to be monitored in a given monitoring
cycle and a number of monitoring cycles may be executed in a given
correlation cycle. The network node may also receive reported
monitoring results and update a correlation table to facilitate the
correlation process. The network node may be implemented in, for
example, an OMM (optical monitoring module) or a network analyzer
or a combination or both.
[0026] Additional aspects of the invention will be set forth, in
part, in the detailed description, figures and any claims which
follow, and in part will be derived from the detailed description,
or can be learned by practice of the invention. It is to be
understood that both the foregoing general description and the
following detailed description are exemplary and explanatory only
and are not restrictive of the invention as disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] A more complete understanding of the present invention may
be obtained by reference to the following detailed description when
taken in conjunction with the accompanying drawings wherein:
[0028] FIG. 1 simplified block diagram illustrating selected
components of an exemplary PON (passive optical network) in which
embodiments of the present invention may be advantageously
implemented;
[0029] FIG. 2 is a simplified block diagram illustrating selected
components of a PON implementing an embodiment of an ISM
(intelligent splitter monitor);
[0030] FIG. 3 is a simplified block diagram illustrating selected
components of a network node according to an embodiment of the
present invention;
[0031] FIG. 4 is a flow diagram illustrating a method of
optical-network monitoring according to an embodiment of the
present invention; and
[0032] FIG. 5 is a flow diagram illustrating a method of
optical-network monitoring according to an embodiment of the
present invention.
DETAILED DESCRIPTION
[0033] Embodiments of an optical network monitoring apparatus,
system, and method are described herein, and are expected to be of
particular advantage when implemented to correlate downstream
devices in the network to optical splitter ports with which they
are associated. Optical networks are useful as, for example, PONs
(passive optical networks) and similar access networks and data
centers.
[0034] FIG. 1 is a simplified block diagram illustrating selected
components of an exemplary PON (passive optical network) 100 in
which embodiments of the present invention may be advantageously
implemented. Note that PON 100 may, and in many implementations
will, include additional components, and the configuration shown in
FIG. 1 is intended to be exemplary rather than limiting.
[0035] In the example of FIG. 1, the network 100 includes an OLT
(optical line terminal) 110, typically located at a CO (central
office) 120. The OLT 110 communicates with ONUs (optical network
units) 130a, 130b . . . 130n using an optical source via an optical
path such as a fiber optical cable 140. Downstream data from the
OLT 110 are addressed to one or more of the ONUs 130, each of which
is configured to recognize data addressed to it. The optical cable
140 connects to a splitter/combiner 150 (or for convenience, simply
"splitter").
[0036] The splitter 150 divides the downstream optical signal from
the OLT 110 between a number of downstream ports, for example ports
155a, 155b . . . 155n. From the splitter ports, the divided signal
is carried to ONUs 130a, 130b . . . 130n via access fibers 160a,
160b . . . 160n. Each ONU 130 may also transmit upstream data to
the OLT 110 via the access fibers 160a, 160b . . . 160n. Optical
signals from each ONU 130 are combined by the splitter 150 and
propagate from there to the OLT 110 via optical cable 140.
[0037] As used herein, "ONU" is intended to be broadly construed to
include ONTs (optical network terminals) and other CPE (customer
premises equipment). In some networks (not shown), other downstream
devices, for example another optical splitter/combiner, may be
present on the optical path as well. Note that not all access
fibers in a network are connected to an authorized downstream
device, but are generally available should the need arise to do so.
Naturally, no upstream transmissions are expected on idle access
fibers.
[0038] For those access fibers that are connected to ONUs (or other
downstream devices), the service provider may need to identify the
specific port 155 with which a particular ONU 130 is in
communication, for example, an when end-user of one of the ONUs 130
experiences a service disruption. Sometimes the port is identified
in records generated when the system 100 is installed, maintained
or upgraded. Often, however, such records do not exist or are
inaccurate, and the particular port 155 associated with the
affected ONU 130 cannot be identified without a personal inspection
by a service technician to the site of the splitter 150 and/or the
affected ONU 130 or its associated demarcation point (not
shown).
[0039] If an incorrect port is disconnected during network
servicing, however, service may be disrupted to a user other than
the intended user. In some cases the splitter 150 is located in an
outside plant 125 (for example, a street cabinet) tens of
kilometers from the CO 120, which itself may be some distance from
the affected ONU 130. A coordinated test of the ONU 130 and
identification of a desired splitter port 160 conventionally
typically requires a two-person team, for example one person
located at the site of the splitter 150, and one person located at
the site of the ONU 130 of interest. (Each ONU, of course, is
typically located at a different customer premises.) Thus, the
service call may be time-consuming and expensive.
[0040] FIG. 2 is a simplified block diagram illustrating selected
components of a PON 200 implementing an embodiment of an ISM
(intelligent splitter monitor). Again, note that PON 200 may, and
in many implementations will, include additional components, and
the configuration shown in FIG. 2 is intended to be exemplary
rather than limiting.
[0041] In the embodiment of FIG. 2, OLT 210 is resident in CO 220,
and is in optical communication with ONUs 230a, 230b . . . 230n via
feeder fiber 240, optical splitter 250, and access fibers 260a,
260b . . . 260n, which are each associated with a respective one of
splitter ports 255a, 255b . . . 255n.
[0042] An ISM (intelligent splitter monitor) 270 is implemented in
PON 200 and associated with optical splitter 250. In this
embodiment, ISM 270 includes a microcontroller 272 in communication
with a memory device 274 (optional). Both are preferably
implemented in hardware or software instructions executing on
hardware, or a combination of both. Tap couplers 276a, 276b . . .
276n and photodiode array 278 are used to detect upstream traffic
and identify the downstream splitter port with which it is
associated.
[0043] In this embodiment, ISM 270 also includes a transmitter 280
and receiver 282 for communicating with network nodes in, for
example, a central office. This communication is typically through
not necessarily by optical transmission, as illustrated in FIG. 2.
As is shown there, the ISM preferably communicates with the CO 220
over optical cable 240. The transmitter 280 and receiver 282
facilitate, for example, the reception of instructions at the ISM
270 and the reporting of monitoring results.
[0044] Here is noted that the ISM 270 is preferably implemented in
hardware, and in a particularly preferred embodiment on a single
chip such as a PIC along with the optical splitter/combiner 250. As
such there will be a demarcation or port between an actual optical
fiber cable and another portion of the optical communication path,
such as on the chip itself, but these details are largely omitted
from FIG. 2 for clarity. Where optical connections are evident from
the drawing but not shown in detail, they may in implementation be
supplied by devices now or then known in the art.
[0045] In the embodiment of FIG. 2, ISM 270 is powered in whole or
in part by light transmitted from the CO 220. For this purpose ISM
270 includes a photocell 284 for converting the light energy from
the CO into electrical energy for storage in rechargeable battery
286. Power controller 285 controls the recharging of battery 286
and use of the power by microcontroller 272. In some
implementations, a secondary power source (not shown) may be
provided for use if necessary.
[0046] In this embodiment, operation of the ISM 270 is controlled
by a network analyzer 245, usually located within the CO 220. In
most implementations, the network analyzer 245 will have other
functions as well. In the context of the present invention, network
analyzer 245 directs the OLT 210 to control traffic, for example
directing specific ONUs to temporarily silence upstream
transmissions, and to power the ISM 270. In this embodiment,
network analyzer 295 also coordinates with OMM 290, which
communicates with ISM 270 via receiver 292 and transmitter 294. OMM
290 may, for example, direct the monitoring cycles performed by ISM
270 and receive the monitoring reports.
[0047] It should be noted that the configuration and function of
the components of PON 200 described herein may vary according to
the implementation, for example functions here allocated to one
particular component may in some cases be performed by another.
[0048] FIG. 3 is a simplified block diagram illustrating selected
components of a network node 300 according to an embodiment of the
present invention. In this embodiment, the network node serves a
management function with respect to network monitoring. In this
embodiment, the network node 300 includes a processor 305 and a
memory device 310. Processor 305 and memory device 310 are
implemented in hardware or software instructions executable on a
hardware platform or both. Memory device 310 is non-transitory in
the sense of not being wholly embodied in a propagating signal,
unless explicitly stated to the contrary in a particular
embodiment. In a preferred embodiment, processor 305 is configured
provide the management function by executing instructions and data
stored on memory device 310.
[0049] In the embodiment of FIG. 3, network node also includes
correlation table 315 for tracking the downstream devices
operational on the network. Preferably the table may be used to
create a sequential list of some or all of these devices, and to
keep track (incrementally if applicable) of those downstream
splitter ports through which the network node is communicating with
one (or in some cases a number of) downstream devices. As will be
explained below, incremental tracking may involve associating or
disassociating each device with in the table with several splitter
ports until subsequent monitoring cycles, as necessary, permit a
unique (or at least satisfactory) association.
[0050] In the embodiment of FIG. 3, the network node also includes
a correlation module 320 for managing the operations of a
correlation cycle including selecting sets and subsets of devices
to be enabled and disabled for selected monitoring cycles, as
explained in more detail below, for directing operations of an ISM
associated with the optical splitter, and for receiving monitoring
reports from the ISM and updating the correlation table 315.
Correlation table 315 and correlation module 320 are implemented in
hardware or software instructions executable on a hardware platform
or both unless explicitly stated to the contrary in a particular
embodiment.
[0051] Note that other components may and often are present in
network node 300 as well. In addition, some of the components may
be divided in some implementations into separate modules or
alternatively combined. The modules of the network node 300 may
reside in a single physical location or be distributed among more
than one, for example the OMM 290 and the network analyzer 295
shown in FIG. 2.
[0052] In preferred embodiments, network node 300 is configured to
perform one or more of the methods described herein, for example
those described below in reference to FIGS. 4 and 5.
[0053] FIG. 4 is a flow diagram illustrating a method 400 of
optical-network monitoring according to an embodiment of the
present invention. This embodiment will for convenience be
described in terms of a PON having a plurality of ONUs in optical
communication with a central office via an optical splitter,
although the invention is applicable in other optical environments
as well. At START it is presumed that the necessary components are
available and operational according to at least this embodiment. In
particular, it is presumed that an ISM has been provided and
activated, for example the ISM depicted in FIG. 2. The process then
begins with selecting (405) a plurality (but not all) of ONUs and
directing (410), un-selected ONUs to cease upstream transmissions
on the PON. In the context of a PON, such directions may be
accomplished using PLOAM (physical layer operations,
administration, and maintenance) messages.
[0054] In this embodiment, following the silencing of un-selected
ONUs, the ISM monitors (step 415) for upstream activity on the
downstream (ONU-facing) ports of the optical splitter. Note that in
most implementations, the communication channel associated with
each downstream splitter port is monitored. The monitoring
operation is preferably performed as quickly as possible, but needs
to be long enough in duration to provide a reliable certainly that
all active ports associated with a selected ONU have been
identified. The results of the monitoring are then reported (step
420), in most cases by the ISM to a managing network node in the CO
such as OMM 290 depicted in FIG. 2. If necessary, the un-selected
ONUs are then directed (step 425) to resume normal operation.
[0055] Note that as used herein, "selected" devices refer to those
to be left fully operational during a monitoring cycle while
"unselected" devices are directed to temporarily cease upstream
transmissions. In actual practice, of course, the "selected
devices" to be left fully operational may be "selected" as that
term is used here and in the claims by "selecting" other devices to
be to be silenced.
[0056] The reported results are used to update (step 430) a
correlation table, for example in an OMM. The correlation table
normally includes all of the ONUs that have been identified as
operating on the PON and a notation or flag associating or
disassociating each ONU with particular ports. The selected ports
referred to above, for example, may but are not necessarily
associated with ports that were active during the monitoring cycle
of steps 410 to 425. Unselected ONUs may of course be disassociated
from those ports. A single monitoring cycle may not, and in most
implementations will not, be able to uniquely correlate all ONUs
with a particular port.
[0057] In the embodiment of FIG. 4, a determination (step 435) is
then made as to whether a correlation of operating ONUs to
downstream optical splitter ports has been achieved. In most cases,
the goal will be to achieve a full correlation, that is, a unique
one to one correspondence (sometimes referred to as a "bijective
assignment") of ONUs to splitter ports, but in some
implementations, this may not be necessary (for example if a
determination can be made as to one ONU of particular interest). In
this embodiment, the determination is made by examining the
correlation table.
[0058] If it is determined at step 435 that a satisfactory
correlation has been achieved, then the process continues, for
example, by allowing the ISM to enter sleep mode until a need to
update or confirm the correlations occurs or a period of time has
passed if a standard monitoring scheduled has been established (not
separately shown). If, on the other hand, it is determined at step
435 that correlation has not been achieved, the process returns to
step 405 for the selection of another plurality of ONUs and a
repeat of the steps for directing (step 410) unselected ONUs to
cease upstream transmission, monitoring downstream splitter ports
(step 415), reporting (step 420), updating the correlation table
(step 430) and determining (step 435) if a correlation has been
achieved. Of course, if necessary, the ONUs are again directed
(step 425) to return to normal operation as well.
[0059] As should be apparent, the selection process at step 405
after a determination that correlation has not been achieved should
select a different subset of ONUs than has been previously selected
(in this correlation cycle), otherwise in almost all cases the
monitoring results will simply be replicated. A preferred
methodology for making such selections will be described below.
[0060] FIG. 5 is a flow diagram illustrating a method 500 of
optical-network monitoring according to an embodiment of the
present invention. At START it is presumed that the necessary
components are available and operational according to at least this
embodiment. In particular, it is presumed that an ISM has been
provided and activated, for example the ISM depicted in FIG. 2.
[0061] The process according to this embodiment then begins with
determining (step 505) the identity of end devices that are active
on the network. In normal operation for many optical networks, such
as a PON, a network node such as an OLT will communicate with each
of the end devices (such as ONUs) operationally connected to one of
the access fibers or other optical communication channels
downstream of the optical splitter in question (see, for example,
FIGS. 1 and 2), beginning with some form or authorization,
recognition, or ranging protocol. The identity of each operational
end device is obtained as part of this process and may be stored
(step 510) in a correlation table.
[0062] The process according to this embodiment then continues with
defining (step 515) a collective-monitoring set. The
collective-monitoring set consists of at least a portion of the
plurality of downstream devices as well as any dummy downstream
devices necessary to give the set 2.sup.n members, wherein n is a
positive integer. The collective-monitoring set preferably includes
all of the downstream devices that are to be collectively monitored
and correlated in this correlation cycle. In this preferred
embodiment, the collective-monitoring set does not include those
end devices that will be individually monitored and correlated (as
will be discussed below). It may also exclude devices for which a
port association is somehow known, or on the other hand not desired
at this time.
[0063] The collective-monitoring set may be identified or stored
(not separately shown), for example in a correlation table. In
effect, the collective monitoring set forms a sequential listing of
2.sup.n devices, where n is an integer equal to or greater than m,
the number of downstream devices to be collectively monitored in
the collective monitoring of a particular correlation cycle.
[0064] In the embodiment of FIG. 5, the process then continues with
selecting (step 520) a plurality of subsets from the
collective-monitoring set, with each subset having more than one
but less than all of the end devices in the collective-monitoring
set. In preferred embodiments, each subset includes one-half of the
end devices in the collective-monitoring set. A plurality of ports
monitoring cycles, each applying a different one of the plurality
of subsets, is then executed (step 525).
[0065] In this embodiment, each port monitoring cycle includes (not
separately shown) directing those end devices not selected in the
respective subset to cease upstream transmissions and monitoring
upstream traffic. As mentioned above, the monitoring may be
performed by an ISM which detects those downstream splitter ports
that are active during a particular port monitoring cycle, that is,
those that are receiving upstream transmissions from end
devices.
[0066] In the embodiment of FIG. 5, the monitoring results are then
reported (step 530). Note that the monitoring results may be
reported after each port measurement cycle, or at the end of the
correlation cycle when all desired monitoring has been completed,
or at any time in between. In this embodiment, it may presumed that
the unselected end devices are directed to cease upstream
transmissions only for a limited duration, that is, long enough for
the monitoring to be properly performed, and therefore do not need
to be directed to resume normal upstream operations. Alternatively,
they may be affirmatively directed (not shown in FIG. 5) to
continue after each monitoring cycle. The end devices may of course
continue to receive downstream transmissions throughout the
process, absent some reason for directing them otherwise.
[0067] It is here noted that if the subsets for the port
measurement cycles are properly selected, the number of port
measurement cycles may be anticipated. Preferred processes for
selecting the subsets from the collective-monitoring set
follows.
[0068] In a preferred embodiment, a first selected subset includes
only the first half of the end devices in the collective-monitoring
set--"first half" referring for convenience to the sequential
listing mentioned above. A second subset may then include only the
first half of these and the first half of those not in the first
subset. Subsequent subsets are selected in the same fashion,
selecting the first half of each selected group and the first half
of each unselected group in the previous subset. When this method
is used, log.sub.2(n) subsets will usually be needed for complete
correlation of n devices. An example for n=8 follows (with end
devices indicated by sequence numbers; actually device IDs may be
stored in the table but are not shown here).
TABLE-US-00001 Device 1.sup.st subset 2.sup.nd subset 3.sup.rd
subset 0 .cndot. .cndot. .cndot. 1 .cndot. .cndot. 2 .cndot.
.cndot. 3 .cndot. 4 .cndot. .cndot. 5 .cndot. 6 .cndot. 7
[0069] Note that while the subsets are selected in a certain order
for convenience in description, they may be used for any
measurement cycle, provided each subset is used only once in the
correlation cycle. Note also that the subset-forming process may be
varied somewhat from the description above, for example by
selecting the second half of a previous group rather than the
first, but some consistency is needed to ensure that only the
minimum number of subsets is needed for correlation.
[0070] In another preferred embodiment, subset selection may be
described in a different way by assigning to the list of devices a
log.sub.2(n)-bit binary sequence number. The first and subsequent
subsets are then formed by selecting the devices associated with a
"0" value in the respective (1.sup.st, 2.sup.nd, etc.) column of
the binary sequence number. As above, of course, in performing the
correlation, the subsets thus formed could be cycled through in any
order, and the selection could be based, for example, on "1" values
rather than "0".
TABLE-US-00002 Device 1.sup.st subset 2.sup.nd subset 3.sup.rd
subset 0 000 .cndot. .cndot. .cndot. 1 001 .cndot. .cndot. 2 010
.cndot. .cndot. 3 011 .cndot. 4 100 .cndot. .cndot. 5 101 .cndot. 6
110 .cndot. 7 111
[0071] In yet another preferred embodiment, this process may be
expressed mathematically as follows, referring to the sequential
device numbers for n devices. In this context, as above, "group"
refers to devices that are directly adjacent to each other in the
sequential listing. Note that in the last selected subset, the
group size is always 1, that is, a single device. Note also that
for this purpose the first and last devices (of the whole list or
any group) are considered adjacent to each other.
TABLE-US-00003 1.sup.st 2.sup.nd 3.sup.rd group subset subset
subset . . . last subset a 0 . . . n/2 - 1 0 . . . n/4 - 1 0 . . .
n/8 - 1 device 0 b n/2 . . . n/2 + n/4 . . . n/4 + device 2 n/4 - 1
n/8 - 1 c n/2 . . . n/2 + device 4 n/8 - 1 d n/4 + n/4 . . . n/2 +
device 6 n/4 + n/8 - 1 . . . . . . . . . (last) device n - 2
[0072] In any case, note that where n is greater than m, the
selection proceeds as above acknowledging that some of the listed
"devices" will be dummy devices. Naturally, dummy devices are not
actual devices and there is no need to direct dummy devices to
cease or resume upstream transmissions. As should be apparent, the
selection of an n large enough to include all m devices but no
larger is the most efficient approach.
[0073] Note also that in some cases, m, the number of active
downstream devices to be collectively monitored in a given
correlation cycle, may not include all downstream devices active on
the optical network. This may be the case where, for example, a
unique correlation has already been made between a downstream
device and a downstream splitter port or where it is more efficient
to correlate one or more devices using another method. This latter
case may occur, for example, where a sequential listing including
all active downstream devices would include a large number of dummy
devices.
[0074] If n does not include the total number of active downstream
devices, measurement cycles with only one device silenced may be
used to perform a complete correlation. In the embodiment of FIG.
5, any port cycles for the individual-monitoring subsets (each
including one device) are executed (step 535) after the
collective-monitoring port cycles. The results of this monitoring
are then reported (step 540). It is noted again, however, that the
reporting step or steps may be performed as desired in a given
implementation.
[0075] It is also noted that the port correlation of a correlation
cycle could be accomplished entirely through the (sole) use of
individual monitoring subsets, but the techniques described herein
are expected in most implementations to be much more efficient,
requiring fewer monitoring cycles in most cases. This may be of
great advantage where, for example, the ISM and optical splitter
are in an outside plant where power is not available except as
supplied from the CO (see FIG. 2).
[0076] In this embodiment, the process then continues, for example,
by allowing the ISM to enter sleep mode until a need to update or
confirm the correlations occurs or a period of time has passed if a
standard monitoring scheduled has been established (not separately
shown).
[0077] Note that the sequences of operation illustrated in FIGS. 4
and 5 represent exemplary embodiments; some variation is possible
without departing from the claims as they are recited. For example,
additional operations may be added to those shown in FIGS. 4 and 5,
and in some implementations one or more of the illustrated
operations may be omitted. In addition, the operations of the
method may be performed in any logically-consistent order unless a
definite sequence is recited in a particular embodiment.
[0078] Although multiple embodiments of the present invention have
been illustrated in the accompanying Drawings and described in the
foregoing Detailed Description, it should be understood that the
present invention is not limited to the disclosed embodiments, but
is capable of numerous rearrangements, modifications and
substitutions without departing from the invention as set forth and
defined by the following claims.
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